The present invention relates to a new and improved method of changing a spatial relationship between bones which are interconnected at a joint in a patient""s body.
It has previously been suggested that joints between bones be fused, that is, surgically immobilized, to promote patient comfort. Thus, U.S. Pat. No. 5,026,373 suggests that a fusion cage be positioned between adjacent vertebrae. Perforations are formed in the cage. The cage is packed with a bone-inducing substance. A method for immobilizing vertebrae is also disclosed in U.S. Pat. No. 5,015,255.
It has previously been suggested that the spatial relationship between portions of a bone in a patient""s body be changed to correct deformities. This may be done by removing a wedge-shaped piece of bone in the manner disclosed in U.S. Pat. No. 5,601,565.
Another method of changing the spatial relationship between portions of a bone in a patient""s body includes forming a slot in the bone. A forked wedge tool is inserted into the slot. A plate is then placed in a central opening in the forked wedge tool and positioned against the bone. The plate is secured to the bone. The forked wedge tool is then removed from the opening. This method of changing the spatial relationship between portions of a bone in a patient""s body is disclosed in U.S. Pat. No. 5,620,448.
A method and apparatus for use in changing a spatial relationship between portions of a bone in a patient""s body is also disclosed in co-pending U.S. patent application Ser. No. 09/109,126, filed Jun. 30, 1998 by Peter M. Bonutti and entitled Method And Apparatus For Use In Operating On A Bone. This application discloses the use of a wedge member to expand a slot formed in a bone. The wedge member is porous and may be coated with and/or contain bone growth promoting material. The wedge member may have a configuration which corresponds to a configuration of a portion of the bone which is engaged by the wedge member.
Alternatively, the wedge member disclosed in the aforementioned application Ser. No. 09/109,126 may have a circular cross sectional configuration with an external thread convolution to enable the wedge member to be moved into an opening in a bone by rotating the wedge member.
A new and improved method and apparatus is provided to change a spatial relationship between bones which are interconnected at a joint in a patient""s body. When this is to be done, an opening is formed in a portion the patient""s body to expose the joint interconnecting the bones. One of the bones is moved relative to the other by expanding at least a portion of the joint with a wedge member. The wedge member is moved into the joint and applies force against the bones. The opening is closed with the. wedge member still disposed in the joint between the bones. Force is then transmitted between the bones through the wedge member to maintain the joint in an expanded condition.
If the joint is to be flexed after being expanded by the wedge member, the wedge member may be connected with only one of the bones. Alternatively, if the joint is to be, immobilized (fused) after inserting the wedge member, the wedge member may be fixedly connected with the bones interconnected at the joint. The wedge member may be porous and may be coated with and/or contain bone growth promoting material.
One embodiment of the wedge member has major side surfaces extending between thick and thin end portions of the wedge member. The wedge member is moved into the joint with the thin end portion leading. As the wedge member is moved into the joint, the thick trailing end portion of the wedge member expands the joint.
In another embodiment of the invention, the wedge member is rotated relative to the joint to expand the joint. The wedge member may have a circular cross sectional configuration and an external thread convolution which extends from a thin leading end of the wedge member to a thick trailing end of the wedge member. The wedge member is pressed into the joint and rotated to cause the wedge member to expand the joint.
In another embodiment of the invention, the wedge member has surface areas which are relatively close together and other surface areas which are relatively far apart. The wedge member is moved into the joint with the surface areas which are close together engaging the adjacent bones. The wedge member is then rotated to apply force against the adjacent bones to expand the joint. The wedge member may be rotated about its central axis to apply forced against the bones and expand the joint.
Alternatively, the wedge member may be rotated about a location where the wedge member engages one of the bones.
Regardless of which embodiment of the wedge member is selected, the wedge member may be used with any one of the many different bones and joints in a patient""s body. The wedge member may be utilized at joints in a patient""s wrist, ankle, hand, foot, back or other portions of the patient""s body. The wedge member may be particularly advantageous when a joint between vertebrae in patient""s back is to be immobilized. One or more wedge members may be used to expand a joint and transmit force between bones.